Heart and Stroke Foundation Center for Stroke Recovery

Canada

Heart and Stroke Foundation Center for Stroke Recovery

Canada

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Mansfield A.,Heart and Stroke Foundation Center for Stroke Recovery | Mansfield A.,Sunnybrook Health science Center | Mansfield A.,University of Toronto | Mochizuki G.,Heart and Stroke Foundation Center for Stroke Recovery | And 7 more authors.
Neurorehabilitation and Neural Repair | Year: 2012

Background. Stroke-related sensorimotor impairment potentially contributes to impaired balance. Balance measures that reveal underlying limb-specific control problems, such as a measure of the synchronization of both lower limbs to maintain standing balance, may be uniquely informative about poststroke balance control. Objective. This study aimed to determine the relationships between clinical measures of sensorimotor control, functional balance, and fall risk and between-limb synchronization of balance control. Methods. The authors conducted a retrospective chart review of 100 individuals with stroke admitted to inpatient rehabilitation. Force plate-based measures were obtained while standing on 2 force plates, including postural sway (root mean square of anteroposterior and mediolateral center of pressure [COP]), stance load asymmetry (percentage of body weight borne on the less-loaded limb), and between-limb synchronization (cross-correlation of the COP recordings under each foot). Clinical measures obtained were motor impairment (Chedoke-McMaster Stroke Assessment), plantar cutaneous sensation, functional balance (Berg Balance Scale), and falls experienced in rehabilitation. Results. Synchronization was significantly related to motor impairment and prospective falls, even when controlling for other force plate-based measures of standing balance control (ie, postural sway and stance load symmetry). Conclusions. Between-limb COP synchronization for standing balance appears to be a uniquely important index of balance control, independent of postural sway and load symmetry during stance. © 2012 The Author(s).


Hendrickson J.,University of Waterloo | Hendrickson J.,Toronto Rehabilitation Institute | Patterson K.K.,Toronto Rehabilitation Institute | Patterson K.K.,University of Western Ontario | And 9 more authors.
Gait and Posture | Year: 2014

Spatial and temporal gait asymmetry is common after stroke. Such asymmetric gait is inefficient, can contribute to instability and may lead to musculoskeletal injury. However, understanding of the determinants of such gait asymmetry remains incomplete. The current study is focused on revealing if there is a link between asymmetry during the control of standing balance and asymmetry during walking. This study involved review of data from 94 individuals with stroke referred to a gait and balance clinic. Participants completed three tests: (1) walking at their usual pace; (2) quiet standing; and (3) standing with maximal loading of the paretic side. A pressure sensitive mat recorded placement and timing of each footfall during walking. Standing tests were completed on two force plates to evaluate symmetry of weight bearing and contribution of each limb to balance control. Multiple regression was conducted to determine the relationships between symmetry during standing and swing time, stance time, and step length symmetry during walking. Symmetry of antero-posterior balance control and weight bearing were related to swing time and step length symmetry during walking. Weight-bearing symmetry, weight-bearing capacity, and symmetry of antero-posterior balance control were related to stance time symmetry. These associations were independent of underlying lower limb impairment. The results support the hypothesis that impaired ability of the paretic limb to control balance may contribute to gait asymmetry post-stroke. Such work suggests that rehabilitation strategies that increase the contribution of the paretic limb to standing balance control may increase symmetry of walking post-stroke. © 2013 Elsevier B.V.


Mansfield A.,University of Toronto | Mansfield A.,Heart and Stroke Foundation Center for Stroke Recovery | Inness E.L.,University of Toronto | Wong J.S.,University of Toronto | And 4 more authors.
Neurorehabilitation and Neural Repair | Year: 2013

Background. Individuals with stroke fall more often than age-matched controls. Although many focus on the multifactorial nature of falls, the fundamental problem is likely the ability for an individual to generate reactions to recover from a loss of balance. Stepping reactions to recover balance are particularly important to balance recovery, and individuals with stroke have difficulty executing these responses to prevent a fall following a loss of balance. Objective. The purpose of this study is to determine if characteristics of balance recovery steps are related to falls during inpatient stroke rehabilitation. Methods. We conducted a retrospective review of individuals with stroke attending inpatient rehabilitation (n = 136). Details of falls experienced during inpatient rehabilitation were obtained from incident reports, nursing notes, and patient interviews. Stepping reactions were evoked using a "release-from-lean" postural perturbation. Poisson regression was used to determine characteristics of stepping reactions that were related to increased fall frequency relative to length of stay. Results. In all, 20 individuals experienced 29 falls during inpatient rehabilitation. The characteristics of stepping reactions significantly related to increased fall rates were increased frequency of external assistance to prevent a fall to the floor, increased frequency of no-step responses, increased frequency of step responses with inadequate foot clearance, and delayed time to initiate stepping responses. Conclusions. Impaired control of balance recovery steps is related to increased fall rates during inpatient stroke rehabilitation. This study informs the specific features of stepping reactions that can be targeted with physiotherapy intervention during inpatient rehabilitation to improve dynamic stability control and potentially prevent falls. © The Author(s) 2013.


Miyasike-daSilva V.,University of Waterloo | McIlroy W.E.,University of Waterloo | McIlroy W.E.,Toronto Rehabilitation Institute | McIlroy W.E.,Heart and Stroke Foundation Center for Stroke Recovery
PLoS ONE | Year: 2012

Although the visual system is known to provide relevant information to guide stair locomotion, there is less understanding of the specific contributions of foveal and peripheral visual field information. The present study investigated the specific role of foveal vision during stair locomotion and ground-stairs transitions by using a dual-task paradigm to influence the ability to rely on foveal vision. Fifteen healthy adults (26.9±3.3 years; 8 females) ascended a 7-step staircase under four conditions: no secondary tasks (CONTROL); gaze fixation on a fixed target located at the end of the pathway (TARGET); visual reaction time task (VRT); and auditory reaction time task (ART). Gaze fixations towards stair features were significantly reduced in TARGET and VRT compared to CONTROL and ART. Despite the reduced fixations, participants were able to successfully ascend stairs and rarely used the handrail. Step time was increased during VRT compared to CONTROL in most stair steps. Navigating on the transition steps did not require more gaze fixations than the middle steps. However, reaction time tended to increase during locomotion on transitions suggesting additional executive demands during this phase. These findings suggest that foveal vision may not be an essential source of visual information regarding stair features to guide stair walking, despite the unique control challenges at transition phases as highlighted by phase-specific challenges in dual-tasking. Instead, the tendency to look at the steps in usual conditions likely provides a stable reference frame for extraction of visual information regarding step features from the entire visual field. © 2012 Miyasike-daSilva, McIlroy.


Bolton D.A.E.,University of Waterloo | Bolton D.A.E.,Heart and Stroke Foundation Center for Stroke Recovery | Staines W.R.,University of Waterloo | Staines W.R.,Heart and Stroke Foundation Center for Stroke Recovery
Neuropsychologia | Year: 2014

Objectives: To investigate the role of the prefrontal cortex in attention-based modulation of cortical somatosensory processing. Methods: Six prefrontal stroke patients were compared with eleven neurologically intact older adults during a vibrotactile discrimination task. All subjects attended to stimuli on one digit while ignoring distracter stimuli on a separate digit of the same hand. Subjects were required to report infrequent targets on the attended digit only. Throughout testing electroencephalography was used to measure event-related potentials for both task-relevant and irrelevant stimuli. Results: Prefrontal patients demonstrated significant changes in cortical somatosensory processing based on attention compared to age-matched controls. This was evident both in early unimodal somatosensory processing (i.e. P100) and in later cortical processing stages (i.e. long-latency positivity). Moreover, there was a tendency towards a tonic loss of inhibition over early somatosensory cortical processing (i.e. P50). Conclusions: The attention-based modulation noted for neurologically intact older adults was absent in prefrontal lesion patients. Significance: The present study highlights the important role of prefrontal regions in sustaining inhibition over early sensory cortical processing stages and in modifying somatosensory transmission based on task-relevance. Notably these deficits extend beyond those previously shown to occur as a function of age. © 2014 Elsevier Ltd.


Langdon K.D.,Memorial University of Newfoundland | Langdon K.D.,Heart and Stroke Foundation Center for Stroke Recovery | Granter-Button S.,Memorial University of Newfoundland | Harley C.W.,Memorial University of Newfoundland | And 7 more authors.
Journal of Cerebral Blood Flow and Metabolism | Year: 2013

Dementia is a major cause of morbidity in the western society. Pharmacological therapies to delay the progression of cognitive impairments are modestly successful. Consequently, new therapies are urgently required to improve cognitive deficits associated with dementia. We evaluated the effects of physical and cognitive activity on learning and memory in a rat model of vascular dementia (VasD). Male Sprague-Dawley rats (6 months old) were exposed to either regular chow or a diet rich in saturated fats and sucrose and chronic bilateral common carotid artery occlusion or sham surgery. First, this model of VasD was validated using a 2 × 2 experimental design (surgery × diet) and standard cognitive outcomes. Next, using identical surgical procedures, we exposed animals to a paradigm of cognitive rehabilitation or a sedentary condition. At 16 weeks post surgery, VasD animals demonstrated significant learning and memory deficits in the Morris water maze, independent of diet. Rehabilitation significantly attenuated these cognitive deficits at this time point as well as at 24 weeks. Further, rehabilitation normalized hippocampal CA1 soma size (area and volume) to that of control animals, independent of cell number. Importantly, these findings demonstrate beneficial neuroplasticity in early middle-aged rats that promoted cognitive recovery, an area rarely explored in preclinical studies. © 2013 ISCBFM All rights reserved.


Makedonov I.,Heart and Stroke Foundation Center for Stroke Recovery | Makedonov I.,University of Toronto | Black S.E.,Heart and Stroke Foundation Center for Stroke Recovery | Black S.E.,University of Toronto | And 4 more authors.
European Journal of Neurology | Year: 2013

Background: White matter hyperintensities (WMH) are associated with aging and are prevalent in various brain pathologies. The purpose of the current study was to characterize WMH perfusion in age-matched elderly controls (ECs) and patients with Alzheimer's disease (ADs). Methods: Fifty ECs (23 men) and 61 ADs (33 men) underwent magnetic resonance imaging (MRI), 99mTc-ECD single-photon emission computed tomography (SPECT) and cognitive testing. Brain tissue type was classified on T1 weighted images, and WMH were identified on interleaved proton density/T2 weighted images. Co-registered MR images were used to characterize SPECT perfusion patterns. Results: WMH perfusion was lower than normal appearing white matter (NAWM) perfusion (P < 0.001) in both EC and AD groups. There was no WMH perfusion difference between groups when considering the mean perfusion from all WMH voxels (P > 0.43). However, locations that were likely to be considered WMH tended to have lower perfusion in ADs compared with ECs. Perfusion gradients along watershed white matter regions were significantly different between EC and AD groups (P < 0.05). A relationship was found between the volume of a WMH lesion and its mean perfusion (P < 0.001) in both ECs and ADs. Conclusion: Global WMH were hypoperfused compared with NAWM to the same degree in EC and AD participants, which suggests a common WMH etiology between groups. However, white matter locations that were likely to contain WMH tended to be hypoperfused in ADs compared with healthy aging. This finding is suggestive of AD-specific pathology that reduces the perfusion at anatomic locations susceptible to the formation of WMH through either the neurodegenerative process or AD-related vasculopathy or both. © 2012 The Author(s) European Journal of Neurology © 2012 EFNS.


Lake E.M.R.,University of Toronto | Bazzigaluppi P.,University of Toronto | Stefanovic B.,University of Toronto | Stefanovic B.,Sunnybrook Research Institute | Stefanovic B.,Heart and Stroke Foundation Center for Stroke Recovery
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2016

Ischaemic stroke is the leading cause of adult disability worldwide.Effective rehabilitation is hindered by uncertainty surrounding the underlying mechanisms that govern long-term ischaemic injury progression.Despite its potential as a sensitive non-invasive in vivo marker of brain function that may aid in the development of new treatments, blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) has found limited application in the clinical research on chronic stage stroke progression.Stroke affects each of the physiological parameters underlying the BOLD contrast, markedly complicating the interpretation of BOLD fMRI data.This review summarizes current progress on application of BOLD fMRI in the chronic stage of ischaemic injury progression and discusses means by which more information may be gained from such BOLD fMRI measurements.Concomitant measurements of vascular reactivity, neuronal activity and metabolism in preclinical models of stroke are reviewed along with illustrative examples of post-ischaemic evolution in neuronal, glial and vascular function.The realization of the BOLD fMRI potential to propel stroke research is predicated on the carefully designed preclinical research establishing an ischaemia-specific quantitative model of BOLD signal contrast to provide the framework for interpretation of fMRI findings in clinical populations. © 2016 The Author(s).


Clarke J.,Memorial University of Newfoundland | Clarke J.,Heart and Stroke Foundation Center for Stroke Recovery | Langdon K.D.,Memorial University of Newfoundland | Langdon K.D.,Heart and Stroke Foundation Center for Stroke Recovery | And 4 more authors.
Journal of Cerebral Blood Flow and Metabolism | Year: 2014

Early poststroke rehabilitation effectively improves recovery of function, likely by engaging multiple plasticity processes through use-dependent activation of neural circuits. The loci of such neuroplastic reorganization have not been examined during the initial phase of behavioral recovery. In the current study, we sought to evaluate sub-components of rehabilitation and to identify brain sites first engaged by early rehabilitation. Rats were subjected to endothelin-1 ischemia and placed in either enriched environment (EE), daily reach training (RT), combination of enriched environment and reach training (ER), or standard housing (ST) starting 7 days post ischemia. Functional and histopathological assessments were made after 2, 5, and 10 days of treatment. Animals exposed to 10 days of ER treatment exhibited significantly more use-dependent neuronal activity (FosB/ΔFosB expression) in perilesional cortex than those exposed to EE, RT, or ST treatments. Similar trends were observed in both perilesional striatum and contralesional forelimb motor cortex. This use-dependent plasticity was not explained by differences in neuronal death, inflammation, or lesion volume. The increased activity likely contributes to the neuroplastic changes and functional recovery observed after extended periods of rehabilitation. Importantly, EE or RT alone did not lead to enhanced activity suggesting that combination therapy is necessary to promote maximum recovery. © 2014 ISCBFM All rights reserved.


Al-Khindi T.,University of Toronto | MacDonald R.L.,St Michaels Hospital | MacDonald R.L.,University of Toronto | MacDonald R.L.,Li Ka Shing Knowledge Institute | And 4 more authors.
Stroke | Year: 2010

Background and Purpose-: Aneurysmal subarachnoid hemorrhage (aSAH) is a medical emergency characterized by the accumulation of blood in the subarachnoid space surrounding the brain. The acute treatment of aSAH is well documented but less is known about the long-term effects of aSAH on cognition and day-to-day functioning. Methods-: We reviewed all studies in the past 10 years that have focused on the effects of aSAH on cognition and day-to-day functioning. Results-: Sixty-one empirical studies examining cognitive and functional outcome in patients with aSAH met inclusion criteria. Survivors of aSAH commonly experience deficits in memory, executive function, and language. These cognitive impairments interact to affect patients' day-to-day functioning, including activities of daily living, instrumental activities of daily living, return to work, and quality of life. Deficits in cognition and day-to-day functioning are further compounded by depression, anxiety, fatigue, and sleep disturbances. Conclusions-: Much remains to be learned about the brain changes underlying cognitive and functional deficits, including the role of diffuse brain damage and secondary complications like vasospasm and elevated intracranial pressure. A consideration of these issues is necessary to obtain a better understanding of how aSAH affects cognition and day-to-day functioning in the long-term. © 2010 American Heart Association, Inc.

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